If we talk about cash,.then it is obvious it would become more difficult to control. Nothing stops a group of teens with cash on their hands from gambling their parents money away and not getting caught.
Are you talking about offline casinos? And being a licensed casinos, not a shady ones? They I would say that those teens with cash in their hands gambling career would end at the entrance of the casino, as guards wont let them gamble. I think not a single casino would want to risk their reputation and licenses in exchange for lunch money. But, nothing stops those teens from gambling between themselves. Play cards are in free access, and they can place bets on different scenarios between themselves.